How the custom number field in parent issue contain the sum of values of that field from sub-task?

[Miller T. Perez]

I created a custom field named "Cost" in sub-task issue. 

The Cost field in parent task issue does not contain the sum of values for Cost field from sub-tasks. How will I display the sum in parent?

[Gaston Valente]

Miller,

There's no standar way, you can try by using a Script Custom Field with ScriptRunner.

Here's a great answer:

https://community.atlassian.com/t5/Answers-Developer-Questions/Sum-of-values-from-subtasks-using-JIRA-Calculated-Number-Field/qaq-p/538417